What is the absorption half life of a drug?
Absorption is more than 90% complete affer 4 absorption half-lives. The absorption half-life should not be confused with the elimination half-life. Typical absorption half- lives are less than 0.5 hour while elimination half-lives are offen several hours or days.
What is the difference between elimination and clearance?
Clearance is defined as ‘the volume of blood cleared of drug per unit time’. Drug elimination rate is defined as ‘the amount of drug cleared from the blood per unit time’ In first order kinetics, elimination rate is proportional to dose, while clearance rate remains independent of the dose.
What is hepatic clearance?
Hepatic drug clearance can be defined as the volume of blood perfusing the liver that is cleared of the drug per unit of time. There are three major parameters that determine drug elimination by the liver: blood flow through the liver (Q), which reflects drug delivery to the liver.
What is hepatic extraction ratio?
Hepatic extraction ratio is the fraction of the drug entering the liver in the blood which is irreversibly removed (extracted) during one pass of the blood through the liver.
What is hepatic blood flow?
Blood leaves the liver through the hepatic veins. This blood is a mixture of blood from the hepatic artery and from the portal vein. The hepatic veins carry blood to the inferior vena cava—the largest vein in the body—which then carries blood from the abdomen and lower parts of the body to the right side of the heart.
What is hepatic first-pass effect?
The first-pass metabolism or the first-pass effect or presystemic metabolism is the phenomenon which occurs whenever the drug is administered orally, enters the liver, and suffers extensive biotransformation to such an extent that the bioavailability is drastically reduced, thus showing subtherapeutic action (Chordiya …
How do you avoid the first pass effect?
Alternative routes of administration, such as suppository, intravenous, intramuscular, inhalational aerosol, transdermal, or sublingual, avoid the first-pass effect because they allow drugs to be absorbed directly into the systemic circulation.